Where or how do i find the glow dust offering for the shrine od azura?

Answers

Kill a Will'o'Wisp. There's a few near the shrine, or a bunch hang out in the marshes near Leyawiin. They appear more often at night, I think. Be warned: they're more dangerous than they look. Keep your distance.

In early levels before Will-o-Whisps show up, you can find one glow dust downstairs in the Bruma mages guild (must be a member). Some alchemy ingredient vendors may sell it. There might be one in the Leyawiin mages guild. There are also Will-o-wisps as part of the Fighter's Guild Harlun's watch quest.